The unmanned aerial vehicle is able to automatically sow seeds, apply fertilizers, and perform plant-protection spraying operations. When used in plant-protection spraying operation, since the unmanned aerial vehicle is limited to its own battery capacity, certain pesticide liquid may remain in a pesticide tank after the plant-protection operation is completed, and the remaining pesticide liquid in the pesticide tank may affect accuracy of infusing the pesticide tank at the next operation, thereby reducing operation efficiency of the whole vehicle.